Heretofore, a number of patents and publications have disclosed methods and apparatus for the processing of digital images, and are hereby incorporated by reference for their teachings, the relevant portions of which may be briefly summarized as follows:
U.S. Pat. No. 5,408,329 “IMAGE ENHANCEMENT THROUGH DIGITAL DARKNESS CONTROL,” Louis D. Mailloux, Fairport, N.Y.; Brendan C. Casey, Webster, N.Y.; application Ser. No. 08/941,828 filed Sep. 8, 1992, issued Apr. 18, 1995;
U.S. Pat. No. 5,659,399 “METHOD FOR CONTROLLING COMPACT DOT GROWTH,” Ying-wei Lin, Penfield, N.Y.; Martin E. Banton, Fairport, N.Y.; application Ser. No. 08/565,138, filed Nov. 30, 1995, issued Aug. 19, 1997;
U.S. Pat. No. 5,666,470 “METHOD AND APPARATUS FOR APPEARANCE TUNING OF BITMAP IMAGES,” James D. Parker, Rochester, N.Y., application Ser. No. 08/496,556 filed Jun. 29, 1995, issued Sep. 9, 1997;
U.S. Pat. No. 5,687,297 “MULTIFUNCTIONAL APPARATUS FOR APPEARANCE TUNING AND RESOLUTION RECONSTRUCTION OF DIGITAL IMAGES,” Bonnie R. Coonan, Rochester, N.Y.; Anthony M. Frumusa, Penfield, N.Y.; Aron Nacman, Penfield, N.Y.; Francis K. Tse, Rochester, N.Y.; Michael L. Davidson, Rochester, N.Y.; application Ser. No. 08/496,654, filed Jun. 29, 1995, issued Nov. 11, 1997.
U.S. Pat. No. 6,181,438 “METHOD AND APPARATUS FOR DIGITAL IMAGE DARKNESS CONTROL USING QUANTIZED FRACTIONAL PIXELS,” Rosario A. Bracco, Webster, N.Y.; Michael Branciforte, Rochester, N.Y.; David C. Robinson, Penfield, N.Y.; James O. Mitchel, Rochester, N.Y.; Thomas Robson, Penfield, N.Y.; Robert P. Loce, Webster, N.Y.; Hoan N. Nguyen, Fountain Valley, Calif.; Hung M. Pham, San Gabriel, Calif.; Daniel D. Truong, Hawthorne, Calif.; Louis D. Mailloux, Webster, N.Y.; Cathleen J. Raker, Rochester, N.Y.; Sue K. Lam, Rochester, N.Y.; Robert R. Thompson, Jr., Harbor City, Calif.; Farhad D. Rostamian, Malibu, Calif.; Cheryl A. Pence, Cypress, Calif.; application Ser. No. 09/072,122 filed May 4, 1998, issued Jan. 30, 2001;
U.S. Pat. No. 6,297,889 “LOGIC-BASED IMAGE PROCESSING METHOD,” Robert P. Loce, Webster, N.Y.; Michael Branciforte, Rochester, N.Y.; Ying-wei Lin, Penfield, N.Y.; application Ser. No. 09/218,688, filed Dec. 22, 1998, issued Oct. 2, 2001.
The following publications are also believed to represent the general nature of the digital image processing arts. Many techniques can be found in the arts, of which the following are representative and which are hereby incorporated by reference being made thereto. Vector Quantization and Signal Compression, A. Gesho and R. M. Gray, 1991 describes the use of a filter to assign one or more specific code-words to a given sample (e.g. vector quantization). A filter can also assign one or more tags to a center pixel or a new sample value to the center pixel in order to accomplish the overall goal of a restoration or enhancement of a degraded image, as taught by Enhancement and Restoration of Digital Documents, R. P. Loce and E. R. Dougherty, SPIE Press, 1997, and Enhancement of Digital Documents, R. P. Loce and E. R. Dougherty, Electronic Imaging Technology, SPIE Press 1999, and Two-Dimensional Signal and Image Processing, J. S. Lim, Prentice Hall, 1990.
A filter may also be used to assign an array of fewer, more restrictive values to an observation (often referred to as either “quantization,” “thresholding,” or “dithering”) as taught by Digital Halftoning for Printing and Display of Electronic Images, R. P. Loce, P. G. Roetling, and Y. W. Lin, Electronic Imaging Technology, SPIE Press, 1999. Other applications of filters used in signal or image processing include, resolution conversion, object detection, speckle-removal, and edge enhancement. Nonlinear image or signal processing is a general representation of signal or image filtering based on a logical decomposition of a filter into a set of relatively simple operators. Any windowed shift-invariant filter can be represented as a combination of simple operations called hit-or-miss transforms as taught by Nonlinear Filters for Image Processing E. R. Dougherty and J. Astola (eds.), SPIE/IEEE Press, 1999.
In accordance with the present invention, there is provided a method for processing a digital image to alter the darkness thereof, including the steps of: isolating regions of the digital image wherein said regions include a plurality of imaging areas, said regions including those suitable for altering the darkness thereof, and extracting image data therefrom for the pixels in at least one of said regions; using the extracted image data for said region, producing modified image data by modifying data associated with at least one pixel in the region to alter the darkness of said region; and merging the modified image with the digital image to produce an output digital image having at least one region in which the darkness of the image is altered.
In accordance with another aspect of the present invention, there is provided an apparatus for processing a digital image to alter the darkness thereof, including: windowing means for isolating regions of the digital image wherein said regions include a plurality of imaging areas, said regions including those suitable for altering the darkness thereof; memory for storing image data representing pixels in at least one of said regions; means for producing modified image data, using the image data stored in said memory, by modifying data associated with at least one pixel in the region to alter the darkness of said region; and digital circuitry for merging the modified image data with the digital image to produce an output digital image having at least one region in which the darkness of the image is altered.
One aspect of the invention deals with a basic problem in the processing and rendering of digital images. Digital office and production printers are expected to offer digital darkness, toner saver features, and line width control. To be competitive, these designs often support jaggie reduction and rendering techniques that impact xerographic development, such as line width control and compact dot growth. Such features are often enabled using an appearance tuning architecture. Previously, one of two approaches were used: (a) a massive, fixed appearance tuning design that operates upon a large (e.g., 49-pixel) context; or (b) a limited, programmable design that operates upon a small (e.g., 5-pixel) context. However, both of these approaches were incapable of solving problems with the image output terminal that were recognized late in the development cycle. The former was too inflexible while the latter too limited. Hence, it was often necessary to redesign, modify or limit the functionality of digital office and production printers.
This present invention is based on the discovery of techniques and apparatus designs that alleviate this problem—thereby providing a highly programmable and efficient image processing architecture that is able to handle a larger context (larger numbers of pixels). The technique enables the use and re-use of this image processing architecture across many digital office and production printers and related devices, thereby reducing costs.
The techniques and methods described herein are advantageous because they are cost efficient compared to other approaches, and make it unnecessary to have customized darkness control or similar image processing features that are tied to particular digital copying or printing devices. The present invention can be adapted to any of a number of image output terminals or devices. A wide variety of operations can be implemented using these techniques. Each technique can ensure that the image processing features desired, and tuned for the particular characteristics of the image output terminal, can be implemented. As a result of the invention, development time and cost may be significantly reduced while at the same time providing improved capability for image processing, particularly darkness control, for digital copiers and production printers.